The greatest and most mysterious of the dark guilds, self-proclaimed Guardians of the Gates of Heaven
...and Lo, the man stood at the tenfold gates, his life reflected in the cosmic mirror as he stood atop the world - and was found wanting; Not by the stars, but by his own heart, unable to bear the life replayed before it. He had planned for paradise - but in the weakness of his own heart, found only an eternity atop the world; Becoming Takamagahara; The eternal judge of those who pass beyond the gates.
Altogether little is known about the Organizational Structure of Takamagahara - moreso than their allies Necro Shroud and Lethe Labyrinth, precious little has been learned about their membership, internal layout and structure, or otherwise despite centuries of activity, with what little bits that have been gleaned gained from rumors, heresay, or in one case the boasting of Shou Ozawa. They are believed to be an EXTREMELY small guild with a single-digit member count, never operating with more than 10 members at any given time - their members are believed to almost always work alone and rarely in pairs, and their internal structure from what little has been gleamed is tight-knit and semi-familial; though this has mostly been assumed by the organization's use of "Brother" and "Sister" as honorifics attached to the names of their allies in the guild, and may instead simply indicate a more monastic influence on their organizational structure. Because of this, their members are assumed to each have an extraordinary level of power - a theory which has been somewhat confirmed after the seeming recruitment of Shou Ozawa into the ranks of Takamagahara a few centuries prior to the modern day. Additionally, though they may have more than seven members, the mysterious figure known as Brother Seven is believed to be the ruler of Takamagahara - though almost nothing is known about this figure aside from an obvious religious influence, as the number seven has long had religious significance to many faiths(Including that of The Spirit Kings and The Old Gods, for whom it was a number of reverence that referred to the creator, or overdeity).
The culture of Takamagahara is one of utmost secrecy and mystery - the are seemingly unfathomably strict with recruitment of new members(With the only known recruitment of a new member taking place centuries ago during their recruitment of Shou Ozawa to the seat of Brother Six), and keep information quite well seperated between their constituent members. They seem to know each other as well as family, and have likely been sworn to secrecy by each other and their leader in an effort to mask their activities, members, and more. Beyond this, the culture of the Dark Guild Takamagahara is mostly a mystery many seek to know, but few can truly learn about.
The public agenda of Takamagahara is, like so much else about the mysterious Dark Guild, a mystery - the activities of Takamagahara are very poorly documented despite centuries of activity, only appearing briefly at the heads of a number of varied operations ranging from slave trading, organized crime, governmental manipulation and corruption, smuggling, as well as many more. They seem to be unfathomably wealthy, as the Dark Guild, despite its mysterious nature, has the biggest amount of subordinate guilds beneath them as well as a large amount of seemingly normal businesses and other operations, all funded and supported by Takamagahara's seemingly bottomless resources. As such, because of the numerous avenues and activities they have supported and funded over the centuries, little can be gleamed as to their true intentions - they have funded horrific experiments designed to truly return the dead to life, projects to create artificial mechanical life, or even things as simple as explorations of ruins and theft of artifacts uncovered within.
The resources of the dark guild Takamagahara are seemingly infinite - their funding that streams into their hundreds of subordinate dark guilds and dozens of seemingly legal organizations and businesses scattered across Zheng-Kitar has yet to expire despite centuries of operation. Their base of operations, if they possess a central headquarters, cannot be found or traced - further complicating things is the fact that Takamagahara seems to have a place of operations in almost every city and country on Zheng-Kitar, each rotating and changing in regular intervals to prevent tracing or tracking.
Precious little is known of the Dark Guild's history - their own secrecy means those who pursue them only have rumor and superstition to go off of for hints as to their history and/or whereabouts.
By light of the cosmic mirror.
Them? Well, they founded the alliance - for reasons that still aren't entirely clear to me. The biggest and most powerful of the "Big Three", too - Me and Necro Shroud might be good, but challenging them is another matter entirely. We've all heard the rumors. Entire guilds vanishing overnight. Entire towns snuffed out in a single eyeblink. Nasty rumors that make me look like a saint. Lethe Labyrinth has it even worse than us - they're still traumatized after they destroyed a subordinate guild to Takamagahara, and lost their famously secretive guildmaster to assassination the next day. Word of advice - leave 'em alone. Otherwise you'll find the Guardians of the Gates are vengeful fucking gods indeed.
While officially allies under the Raughata Alliance, the treatise which has bound the three largest dark guilds together in a nonaggression pact, Takamagahara and Necro Shroud get along better than many might assume - frequently contracting each other out and aiding each other in difficult jobs, and often working alongside each other on various tasks. They mostly go out of their way to avoid each other otherwise, staying strangely neutral towards each other outside of these periods of cooperation - an oddity among the Dark Guilds.
Wary Allies that avoid each other
While officially allies under the Raughata Alliance, the treatise which has bound the three largest dark guilds together in a nonaggression pact, Takamagahara and Lethe Labyrinth seem to wholly avoid each other - there has never been documented or suspected instances of cooperation between them, and they even seem to go out of their way to not provoke each other...though Lethe Labyrinth seems to be more deferential with its avoidance of Takamagahara than vice-versa.